title: Purification and inhibition studies with anions and sulfonamides of an α-carbonic anhydrase from the Antarctic seal Leptonychotes weddellii.
abstract: A high activity α-carbonic anhydrase (CA, EC 4.2.1.1) has been purified from various tissues of the Antarctic seal Leptonychotes weddellii. The new enzyme, denominated lwCA, has a catalytic activity for the physiologic CO(2) hydration to bicarbonate reaction, similar to that of the high activity human isoform hCA II, with a k(cat) of 1.1×10(6) s(-1), and a k(cat)/K(m) of 1.4×10(8) M(-1) s(-1). The enzyme was highly inhibited by cyanate, thiocyanate, cyanide, bicarbonate, carbonate, as well as sulfamide, sulfamate, phenylboronic/phenylarsonic acids (K(I)s in the range of 46-100 μM). Many clinically used sulfonamides, such as acetazolamide, methazolamide, dorzolamide, brinzolamide and benzolamide were low nanomolar inhibitors, with K(I)s in the range of 5.7-67 nM. Dichlorophenamide, zonisamide, saccharin and hydrochlorothiazide were weaker inhibitors, with K(I)s in the range of 513-5390 nM. The inhibition profile with anions and sulfonamides of the seal enzyme was rather different from those of the human isoforms hCA I and II. The high sensitivity to bicarbonate inhibition of lwCA, unlike that of the human enzymes, may reflect an evolutionary adaptation to the deep water, high CO(2) partial pressure and hypoxic conditions in which Weddell seals spend much of their life.
authors.affiliation: Università degli Studi di Firenze, Dipartimento di Chimica Ugo Schiff, Laboratorio di Chimica Bioinorganica, Rm. 188, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Firenze), Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cincinelli
authors.forename: Tania
authors.initials: T
authors.lastname: Martellini
authors.forename: Alessio
authors.initials: A
authors.lastname: Innocenti
authors.forename: Andrea
authors.initials: A
authors.lastname: Scozzafava
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Supuran
mesh_terms: D000818:Animals; D000838:Anions / Q000737:chemistry* / Q000494:pharmacology; D000864:Antarctic Regions; D024401:Carbonic Anhydrase I / Q000037:antagonists & inhibitors / Q000378:metabolism; D024402:Carbonic Anhydrase II / Q000037:antagonists & inhibitors / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000378:metabolism; D046048:Seals, Earless / Q000378:metabolism*; D013449:Sulfonamides / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000838:Anions; D002257:Carbonic Anhydrase Inhibitors; D020033:Protein Isoforms; D013449:Sulfonamides; D024401:Carbonic Anhydrase I; D024402:Carbonic Anhydrase II; D002256:Carbonic Anhydrases